A recently published patent from Canon details a set of optical formulas for what appears to be an RF 90mm F2. 8L IS Macro lens. Japanese Patent Application Number 2018-205435, first detailed by Northlight Images, is fairly standard as far as patents go, but there is one interesting element worth noting.
The image stabilization elements inside the lens — labelled L12 — are located within the first optical group towards the front of the lens. More often the image stabilization component is towards the center of the lens, but that doesn't appear to be the case here.
This could be for a number of reasons, but the patent text specifically mentions that in order to get the most accurate image stabilization, larger optical components and accompanying motors are needed. As such, the larger front area of the lens makes more sense than the middle of the lens where the optics are more confined, especially with the aperture mechanism located there (represented by 'SP' in the illustrations).
It's also worth noting that the focusing component of the lens is towards the rear of the lens. The patent text says this too is due to the larger focusing motor(s) needed, but it could also have an added benefit of creating a more balanced lens with the heavy image stabilization component towards the front of the lens. As Canon showed the world with its RF 35mm F1. 8 IS STM lens, the RF mount makes it possible to put larger elements and more electronics towards the rear of the lens due to the larger mount size.
. dpreview.com2018-12-28 20:42